I don't think the compression ratio would change significantly based on the number of nodes. That is, the sum of the compressed data on all nodes should have a similar size to the compressed data on a single node. But that's assuming you have optimized projections. Default super projections might not optimize database performance, resulting in slow query performance and low data compression.

Jim Knicely

Note: I work for Vertica. My views, opinions, and thoughts expressed here do not represent those of my employer.